This invention relates to a flexible coupling assembly, which utilizes flexible disc pack elements, for connecting a driving shaft to a driven shaft. A center spacer member is provided which is retained between the shafts in the event of failure of one or more of the flexible disc pack elements.
Where a driving shaft is to be connected to a driven shaft in an end-to-end relationship for transmitting torque from the driving shaft to the driven shaft, a problem of aligning the shafts arises. While, ideally, the shafts should be in perfect alignment, such a condition is difficult to obtain initially and even more difficult to maintain during continued commercial operation. Limited misalignment between two shafts may, however, be accommodated by conventional metal flexible couplings, which routinely employ a hub attached to each shaft, a center spacer member attached between the hubs, and one or more thin metal discs (often fastened together to form a laminated disc pack element) as the portion of the flexible coupling which actually flexes. The discs or disc-pack element are attached between the center member and the hubs and flex to accommodate end float and parallel and/or angular misalignment of the connected shafts. The amount of misalignment manageable by such a flexible coupling is normally limited to several degrees, due to the construction of the coupling and the metallic composition of the flexible element.
The metallic construction of metal flexible couplings normally imparts durability and a long service life, both due to the intrinsic strength of the metallic components and the resistance to corrosion, heat, or other normally encountered conditions or forces which are often detrimental to couplings having flexible elements of rubber and the like.
Problems, however, are also present with above described prior art flexible couplings which utilize flexible disc-pack elements. For example, the disc-pack elements may fail. Such failure of the disc pack element removes the normal holding forces and may thus permit the center spacer member to become broken away from its connection to the flexible coupling with a large amount of kinetic energy. In such a situation, the center spacer member becomes a projectile which could potentially injure personnel and/or damage equipment in the vicinity of the flexible coupling. Flexible couplings are presently available which include hubs that have a portion for insertion into the bore of center spacer member for retaining the center spacer member at the flexible coupling in the event of a disc-pack element failure. Such flexible couplings generally require complex, exacting assembly by a skilled laborer.
Another type of prior art flexible coupling includes a center spacer member assembly which has the flexible disc-pack elements, the center spacer member, and mounting flanges therefor assembled as a unit for attachment between the hub on the driving shaft and the hub on the driven shaft. Because of the integral construction of such a center spacer member assembly, in the event of failure of one of the disc-pack elements, the entire center spacer member assembly must be removed and returned to the manufacturer or to a service center for repair. Another disadvantage of a flexible coupling including an integral center spacer assembly is that the distance between the centers of the two disc-pack elements is typically less than desired, thereby reducing the amount of misalignment that such a flexible coupling having fixed distances between the shafts can accept.
A number of different types of metal flexible couplings are currently available. U.S. Pat. No. 4,055,966, granted to Fredericks, and the Reexamination Certificate number B1 4,055,966 relating thereto, discloses a torque transmission coupling having flexible disc-packs disposed between coupling hubs and a corresponding center spacer member. An alignment pilot ring is fixedly attached on each side of each disc-pack for aligning the hubs with respect to the center spacer member. Bolts passing through a hub, the alignment pilot rings, the flexible disc-pack, and the center spacer member are used in assembling the flexible coupling. U.S. Pat. No. 3,703,817, granted to Orwin, discloses a flexible coupling having two annular, flange-like drive members spaced on either side of a flexible member for attachment between a hub of a driving shaft and a hub of a driven shaft.
Other flexible couplings are disclosed in U.S. Pat. Nos. 2,639,595; 2,712,741; 3,494,147; 3,500,658; 1,454,087; 1,387,532; 2,499,093; 2,745,267; and 4,482,335.